The power of internal combustion engine, Otto Cycle in particular, is directly proportional to the amount of air-fuel mixture which is drawn into and retained within the cylinder for ignition, and all of which is affected by the porting which determines the efficiency of induction and exhaust. Both induction and exhaust are to be optimized for highest efficiency, and flow testing with manometers is practiced in order to show the improved or detrimental affects of changes made to, for example, intake and exhaust ports. And tests have shown that finite changes significantly alter the performance of an engine, that is an opening-up or restriction of a port. Generally, the opening-up of the induction porting is to be desired, but even then there are limits to which this may be practiced. However, it is to be observed that exhaust valves are most often smaller than intake valves, and the volumetric capacity of exhaust ports is commensurately smaller. Accordingly, it is an object of this invention to optimize the restriction of exhaust porting, to be measured and/or tested with "flow-bench" manometers, in order to match the induction capabilities and to tune out turbulence that will otherwise produce flow stagnation.
An original factory port in the head of an engine is but a basic approximation of the most desirable configuration therefor. And there are sophisticated methods of improving these ports, especially the exhaust ports that require filling-in at sharp bends or turns that restrict flow by causing turbulence and resultant stagnation areas. Heretofore, metal has been deposited into the stagnation areas to fill the same and thereby avoid said turbulent restriction, and it has been found that decided flow improvement results even though the actual cross-sectional area of the exhaust is substantially reduced. These filled exhaust ports of reduced area have become known as "D" ports, and which improve flow 15-20% over a conventional round port. Although such port reduction is known to be highly effective, difficulty arises in the application thereof and the ability to tune the same for the highest performance. Therefore, it is an object of this invention to provide exhaust port restriction in the form of inserts mounted to and positioned by the exhaust manifold or header plate thereof, to most advantageously restrict the exhaust ports, individually.
Heretofore, the customizing of engines by "porting" and so called "blue-printing" has involved the removal and replacement of metal bodies throughout the port areas. There are various welding techniques such as the spraying on of molten metal and that of heliarcing, but all subject to warpage of the head castings to which they are applied. Accordingly, it is an object of this invention to avoid port filling of the head per se, by providing inserts associated with the manifold and its header plate. However, exact placement is essential for fine tuning and to this end this invention provides inserts that are placeable and thereafter securable to the manifold at its header plate. In practice, a bare header plate is mounted with these inserts, one for each port and individually positioned for fine tuning with the aid of manometer readings of a flowbench, and thereafter permanently secured in optimum position for use solely with that head to which they are adjusted for optimum flow. The inserts extend from the header plate at the interface with the head and project into the exhaust ports to occupy the stagnation areas thereof.